This application is based upon and claims benefit of priority of Japanese Patent Applications No. 2001-31731 filed on Feb. 8, 2001 and No. 2001-44886 filed on Feb. 21, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a box-shaped casing for containing an electronic control unit therein.
2. Description of Related Art
A substantially box-shaped casing is conventionally used as a casing for containing an electronic control unit. The casing is composed of an upper case having a bottom opening and a bottom plate to close the bottom opening. A printed circuit board on which electronic components are mounted is contained in the casing.
In an automated assembly line, plural upper cases are stacked up and picked up one by one from the top by an arm having a vacuum sucker. In this process, it is required to be able to stack up the upper cases straight and to be able to pick one upper case at a time. In a conventional upper case, to fulfill the above requirements, nuts 52 are positioned at four corners of a bottom fringe of the upper case 51 as shown in FIG. 12. Plural upper cases 51 are stacked up as shown in FIG. 13, so that the nuts 52 provide a certain space between neighboring upper cases 51, thereby preventing the upper case 51 from sticking to another upper case 51 located underneath. It is necessary, however, to give a certain height to the nut 52 in order to provide a required space between neighboring upper cases stacked up. Therefore, the nuts 52 specially made for this purpose have to be used, rendering the manufacturing cost high.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide upper cases which are easily stacked up straight and are able to be picked up one by one with an automated sucker arm, while suppressing the manufacturing cost thereof.
A casing for containing electronic components therein is composed of an upper case and a bottom plate for closing a bottom opening of the upper case. The upper case is substantially box-shaped and includes a ceiling wall, sidewalls and fringe portions connected to the sidewalls. The upper case is so formed that a plurality of upper cases are easily stacked up and separately picked up one by one by an automated arm having a vacuum sucker.
Two sidewalls facing each other are slanted to widen the bottom opening relative to the ceiling wall. The fringe portion connected to the slanted sidewall is bent downward to form a U-shaped portion having an upper wall, a lower wall and a vertical wall connecting the upper wall to the lower wall. A length L1 of the lower wall is made shorter than a length L2 of the upper wall by a gap length L3, so that plural upper cases are easily stacked up. The gap length L3 is made smaller than the lower wall length L1, so that an amount of a horizontal shift of the stacked upper cases is limited to the small gap length L3. The U-shaped portion may be formed by bending the fringe portion upward, and also it may be separated into several portions. Alternatively, instead of forming the U-shaped portion connected to the fringe portion, protrusions projected inwardly may be formed on a vertical guide wall of the fringe portion.
When the upper cases are stacked up, each upper case is spaced from one another by the U-shaped portions or by the inwardly projected protrusions. Accordingly, the upper cases are picked up by the sucker arm one by one, avoiding the upper cases from being stuck together. The protrusions formed on the guide wall of the fringe portion may be engaged with depressions formed on a circuit board to be contained in the casing thereby to correctly position the circuit board in the casing.
According to the present invention, the upper cases are easily stacked up with certain spaces therebetween, while horizontally positioning each upper case, and they are picked up one by one by the sucker arm in the automated assembly line.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.